Image tube



ET AL Nom 1949 G. A. MQRWN IMAGE TUBE Filed May 2, 19417 INVENTORS620885 A. /Voera/v ;241/4 Eau/wa: BY

l TTORNEY Patented Nov. 8, 1949 UNITED STATES FATENT OFFICE IMAGE TUBEApplication May 2, 1947, Serial No. '745,574

6 Claims. 1

This invention relates to electron devices for rendering objects visiblein faintly lighted areas or in total darkness.

In prior art devices, such as disclosed in the co-pending application ofRuedy, Flory and Morton, filed October 5, 1946, Serial No. 701,588, theelectrode structures have been held together inside a glass envelope bywires and glass beads. The electrodes have been made of very thin metaltubing to reduce the mass and minimize movement from the alignedpositions by handling of the tubes. With this construction the pointsand sharp edges gave rise to cold emission when the overall voltage wasaround 5,000 volts. This construction also made it difiicult to maintainproper alignment and spacing between the electrodes while being mountedin the envelope, especially between the photocathode formed on theinside surface of the glass and the adjacent metal tubng electrode.

It is an object of this invention to provide a new type of image devicethat is free of sharp corners and edges to permit use of much highervoltages without cold emission taking place.

Another object of the invention is to mount the electrodes by a ringseal construction that gives a well aligned rigid structure of greatstability.

Another object is to provide an image tube structure that uses a smallerfraction of the aperture of the electron lens near the cathode, thusreducing aberrations.

Another object of the invention is to simplify the electrode system ofan image device and reduce the number of electrodes with no appreciableloss in resolution or image quality.

Other objects will appear in the following description, reference beinghad to the drawing in which the single figure -of the drawing is alongitudinal section of an image tube containing the invention.

Referring to the drawing, the tube comprises a transparent face plate ofappropriate material such as glass for visible light and near infraredWaves or rock salt for far infra-red Waves. This lens may be somewhatconveX outwards as referred to in said co-pending application. A ring I'of metal film is formed on the inside surface of the disc near theperiphery and the photosensitive coating 2 on the inside surface of thedisc makes contact with this ring.

All metal parts are of substantial thickness. say tg of an inch, formedwith well rounded and polished edges. One end of cathode cylinder 3 issealed to the disc I in electrical contact with the metal film ring l'so that the potentials of this tubular electrode and the photocathodeare the same. The rear half of the electrode 3 is of greater diameterthan the first half. Glass tube ii is sealed to the larger end ofelectrode S at one of its ends and at its other end is sealed to theannular fiange 5 of the tubular electrode li which is of the samediameter as the small end of tubular electrode 3. A glass ring 'l issealed to the fiange 5 and to a ring conductor 3, and glass ring 9 issealed to ring 8 and to the fiange le of a shorter tubular electrode Ilof lesser diameter than the tubular electrode 6. A glass tube 12 ofdiameter intermediate those of electrodes 5 and ll is sealed at one endto the fiange ll. The other end of glass tube 52 is sealed to the fiange13 of tubular electrode lt which has an aperture disc ll near the end ofglass tube E2 attached to the fiange ll). The electrodes ll and id areof substantially the same diameter. Glass disc lt is sealed to fiange land its inner surface carries a fluorescent coating il. All the tubularelectrodes and the tubular glass envelopes are coaxial.

One end of an arcuate conductor 25,3 is joined 7 to fiange 5 and itsother end to the ring 8.

Silver material 2! on the conductor 25 is adapted to be vaporized byapplying Voltage between fiange 5 and ring 8. An arcuate conductor 22,carrying caesium material 23, is joined at one end to fiange to and atthe other end to ring 8,

In assembling the parts, the flat glass disc and the glass cylinder IZare fusion sealed in a known way to the fiange |3 of anode lt.Fluorescent coating |1 is then deposited on the inside of disc 16 bysettling or centrifuging it from an aqueous Suspension. This coating maybe willemite or if higher efficiency is desired a phosphor such as zincsulphoselenide may be used. When dried this is then coated with anelectron permeable aluminum film (not shown) by known methods. At thehigh voltages used the latter phosphor even with the aluminum film ismore eflicient than willemite, which would not be true if the lowervoltages of prior art tubes are used. The fiange IO of anode ll isfusion sealed to the open end of glass envelope i2, a mandrel being usedto secure accurate alignment and spacing of electrodes ll and M. This isimportant since the gap between the two electrodes forms the mainelectron lens of the tube. The glass ring 9, metal ring 8, glass ring l,fiange 5 and glass tube 4 are assembled in this order on fiange lt,using a mandrel to obtain accurate axial alignment and spacing of theparts after which they are fusion sealed together. Conductor 20 carryingsilver bead 2| is now welded to fiange and ring 8, conductor 22 carryingcaesium-bearing material 23 is welded to flange i and ring 8. The curvedglass face-plate l is next fusion sealed to the small end of metalenvelope 3 using a mandrel to keep the center of curvature of theface-plate accurately on the axis of the metal tube 3. The ring of metalfilm I' is then applied to make contact between the electrode 3 and theSensitive photo-surface 2 applied as later referred to.

As a final step in the assembling of parts, the larger end of electrode3 i's fusion sealed to the remaining end of glass tube 4 using anexternal jg to keep the parts 3 and 4 concentric and to maintain theproper gap between electrodes 3 and 6. The t'ube may now be exhausted at24 and the silver material 2| vaporized to deposit silver at 2 on theinside of the face plate by applying voltage between fiange 5 and ring8. The caesium material 23 is vaporized by applying voltage betweenflange lu and ring 8 to caesiate the silver coating in a well-known way.

Various voltages and electrode dimensions may be used but as an examplethe electrode 3 may be inch long with a diameter of 1% inches at thesmaller end and a diameter of 1% inches at the larger end. This may'have the voltage of the photocathode, that is, zero volts. Theelectrode 6 may be 1.039 inches long with a diameter of 1% inches andhave a positive voltage of 2000 to 5000 above the cathode. The electrodell may be .171 inch long and 3A in'ch in diameter. This may also 'have apositive voltage of 2000 to 5000 volts. nected to the same positiveterminal. It is used only for a terminal for vaporizing the silver andcaesium material and the dimensions are not important. The electrode |4may be 21/4 inches long and its diameter inch. The voltage of thiselectrode may be 20,000 volts to 35,000 volts. The diaphragm ring 15 maybe spa-ced .360 inch from the free end of electrode Ill and may have anopening with a diameter of 1A; inch. The distance between the free endof electrode 6 from the small end of electrode 3 may be .563 inch. Thefree end of electrode |4 may be spaced 1/8 inch from the plane of theflange Ill. With 20,000 volts on electrode 14, the voltage applied toelectrodes 6 and Il with the above dimensions v may be varied between2000 and 3000 in adjusting the focus of the electrons. To decrease pincushion effect the glass face plate may be a section of a sphere of2.375 inches radius. It will, of course, be understood that the voltagesand dimensions of parts may be altered to fit particular cases.

While certain specific embodiments have been illustrated and described,it will be understood that various changes and modifications may be madetherein without departing from the spirit and scope of the invention.

What we claim as new is:

l. An image device comprising a cathode cylinder, a plate transparent toradiant energy sealed across one end of said cylinder, a cathode on theinside surface of said plate in contact with said cylinder, a pluralityof spaced anode cylinders each having an annular flange, said anodecylinders being place coaxially with the unflanged ends extending in thesame direction, a transparent disc sealed across the end of the anodecylinder farthest from the photocathode, a fluorescent coating on saiddisc and an envelope of The ring 8 may be con- :z

insulating material sealed to said flanges and to the remaining end ofsaid cathode cylinder.

2. An image device comprising a cathode cylinder, a plate transparent toradiant energy sealed across one end of said cylinder, a cathode on theinside surface of said plate in contact with said cylinder, a pluralityof spaced anode cylinders each having an annular fiange at one end, theother ends extending towards said cathode, a disc transparent to lightsealed across the flanged end of the anode cylinder farthest from saidcathode, a fluorescent coating on the inner surface of said disc, glasstubing sealed between the flange of the anode cylinder nearest saidphotocathode and the remaining end of said cathode cylinder and glasstubing sealed between each flange and the succeeding flange whereby allsaid anode cylinders are supported by their flanges.

3. An image device comprising a cathode cylinder, a glass face platesealed across one end of said cylinder, a cathode one the inner surfaceof said face plate in contact with said cylinder, a first anode havingan annular flange at one end, the other end extending toward saidcathode, a glass tube sealed between the remaining end of said cathodecylinder and said flange, a second anode cylinder of lesser diameterthan the first anode cylinder having an annular flange at one end, theother end extending toward the first anode cylinder, two glass rings anda metal washer sealed between said flanges, a third anode cylinder ofsubstantially the same diameter as the second anode cylinder having anannular flange at one end, the other end extending toward and adjacentto the flanged end of the second anode cylinder, a glass tube sealedbetween the last mentioned two flanges, a disc transparent to lightsealed across the flanged end of the third anode and a fiuorescentcoating on the inside of said disc.

4. An image device comprising a cathode cylinder, a plate transparent toradiant energy sealed across one end of said cylinder, a cathode on theinside surface of said plate in contact with said cylinder, a pluralityof spaced anode cylinders each having an annular flange at one end, theother ends extending towards said photocathode, all said cylinders beingcoaxial and free of exposed sharp edges, a transparent disc sealedacross the fianged end of the anode cylinder farthest from thephotocathode and a fluorescent coating on said disc and an envelope ofinsulating material sealed to said fianges and to the remaining end ofsaid cathode cylinder. i

5. An image device comprising a .cathode cylinder, a plate transparentto radiant energy sealed across one end of said cylinder, said platehaving surfaces of revolution convex outwards of the device with Centersin the axis of said cylinder, a cathode on the inside surface of saidplate in contact with said cylinder, a plurality of spaced anodecylinders coaxial with the first cylinder, each having an annular flangeat one end, the other ends extending towards said cathode, a disctransparent to light sealed across the flanged end of the anode cylinderfarthest from said cathode, a fiuorescent coating on the inner surfaceof said disc, glass tubing sealed between the end of the anode cylindernearest said photocathode and the remaining end of said cathode cylinderand glass tubing sealed between each flange and the succeeding flangewhereby all said anode cylinders are supported by their flanges.

6. An image device comprising a cathode cylinder having a portion oflarger diameter than the remaining portion, said portions being joinedby a flange with rounded edges, a glass face plate sealed across thesmaller end of said cylinder having surfaces of revolution convexoutwards of the device with centers in the axis of said cathodecylinder, a cathode on the inner surface of said face plate in contactwith said cylinder, a first anode having an annular fiange at one end,the other end extending toward said 'cathode, a glass tube sealedbetween the remaining end of said cathode cylinder and said flange, asecond anode cylinder of lesser diameter than the first anode cylinderhaving an annular fiange at one end, the other end extending toward thefirst anode cylinder, two glass rings and a metal washer sealed betweensaid fianges, a third anode cylinder of substantially the same diameteras the second anode cylinder having an annular fiange at one end, theother end extending toward and adjacent to the flanged end of the secondanode cylinder, a glass tube sealed between the last mentioned twofianges, all said anode cylinders being coaxial with said cathodecylinder and having rounded edges, a disc transparent to light sealedacross the fianged end of the third anode and a fluorescent coating onthe inside of said disc.

GEORGE A. MORTON.

PAUL RUDNICK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,945,979 Parker Feb. 6, 19342,189,320 Morton Feb. 6, 1940 Certificate of Correcton Patent No.2,487,665 November 8, 1949 GEORGE A. MORTON ET AL.

It is hereby eertified that errors appear in the printed speeificationof the above numbered patent requiring correetion as follows:

Column 3, line 71, for the word uplace read placed; column 4, line 21,for one the read on the;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Oflice.

Signed and sealed this 30th day of May, A. D. 1950.

[sun] THOMAS MURPHY,

A88z'8tant Oommz'esz'oner of Patents.

